UPDATE 1-Jack Welch sets Twitter ablaze with Obama job jab

* Welch stands by his words but says he "not accusing anyone of anything"

(Adds comments from Welch) By Scott Malone and Lucia Mutikani

BOSTON/WASHINGTON, Oct 5 (Reuters) - BOSTON/WASHINGTON, Oct 5 (Reuters) - Jack Welch, the former chairman of General Electric Co , provoked cries of outrage in Washington on Friday when he suggested that the White House manipulated September job figures for political gains.

White House officials dismissed as "ludicrous" a tweet Welch sent to his more than 1.3 million followers that gave the impression President Barack Obama's administration may have rigged the data as a way of recovering from a poor showing at Wednesday night's debate with Mitt Romney, his Republican challenger for the White House.

"Unbelievable jobs numbersï¿½these Chicago guys will do anythingï¿½can't debate so change numbers," Welch said in a posting on Twitter. Obama formerly served as a senator from Illinois.

The tweet was repeated more than 2,000 times, with many mocking posts comparing Welch to New York real estate tycoon Donald Trump, who during his failed bid for the presidency loudly argued that Obama was not born in the United States, and Clint Eastwood, who gave a widely panned speech at the Republican National Convention in August.

Welch, who with his wife, Suzy Welch, writes a column for Reuters, said he is not "accusing anyone of anything." But he stood by his tweet.

Officials in Washington quickly dismissed the idea that the Labor Department report - which showed unemployment falling to a near four-year low of 7.8 percent - could be rigged.

"That's a ludicrous comment. No serious person believes that the Bureau of Labor Statistics manipulates its statistics," said Alan Krueger, chairman of the White House Council of Economic Advisers. "The jobs report and all of their other statistics are prepared by career employees. They use the same process every month. They use the same process for Republican and Democratic administrations."

Later on MSBNC, Welch told host Chris Matthews: "I have no evidence to prove (the BLS numbers were manipulated). I just raised the question." But he said: "You don't think it's coincidental that we've had the biggest job surge since 1983? These numbers defy logic."

The tweet was by no means Welch's first criticism of Obama on his Twitter feed, where he has regularly spoken out in favor of Romney. During the presidential debate in Denver, Colorado, on Wednesday night, Welch tweeted: "HOW can anyone vote for Obama after this performanceï¿½he has demonstrated his incompetence."

"This guy is the guy that's telling me the books are cooked? That's hilarious," said Barry Ritholtz, CEO and director of equity research at Fusion IQ in New York, which manages about $300 million in assets. Ritholtz, one of the first to respond to Welch's tweet, was referring to the allegation that during his tenure at GE, Welch sometimes used the GE Capital finance unit to sell quickly assets such as real estate and ensure that the largest U.S. conglomerate regularly beat Wall Street profit estimates.

Other tweets agreed with Welch's assertion.

"In regards to today's jobs report---I agree with former GE CEO Jack Welch, Chicago style politics is at work here," said Florida Representative Allen West, a Republican, on Twitter.

BLS DEFENDS METHODS

Officials with the Bureau of Labor Statistics defended their methods and findings, noting they are compiled by career civil servants, not political appointees.

"We have done a monthly survey since 1940 and the methods have broadly not changed," said Karen Kosanovich, an economist with the bureau. "Fiddling with the numbers, I don't know how that would be possible."

U.S. Labor Secretary Hilda Solis told CNBC that she was "insulted" by the remark.

As for Welch, 76, he says he went through reviews of more than a dozen companies in different industries this week and none were stronger in the third quarter than they were in the second.